Effect of synergism between sodium alginate and xanthan gum on characteristics of composite film and gloss of areca nut coating

In this study, two polysaccharides of sodium alginate (SA) and xanthan gum (XG) were compounded in proportions of 100:0, 75:25, 50:50, 25:75, 0:100 with 1% total mass concentration and then coated on areca nuts. The effects of their synergistic interactions on the optical appearance of the edible coating were investigated for the first time. Areca nuts coated by 50:50 SA-XG presented the highest gloss (2.69 GU) and maximum spreading coefficient (−33.95 mN/m), indicating the improved wettability of the coating solution on the fruit's surface. The polarized light microscopy exhibited the unique birefringence phenomenon caused by the liquid crystal state, resulting in the better optical properties of the coating. UV–vis transmittance, Fourier transform infrared, and scanning electron microscopy indicated the good compatibility of SA and XG. The SA-XG film was more compactly arranged and had a denser microstructure due to hydrogen bonding. Additionally, the SA-XG combination improved the mechanical properties and water resistance compared to a single polysaccharide films and enhanced the water retention properties for the areca nut coating. Therefore, the SA-XG combination is promising to prepare edible films with improved optical properties for areca nuts.